George p



G. P. BUTLER.

BIT. APPLICATION FILED JUNE 17. 19:6.

F/LTZ H54 //v l/E/V 7-05 550/95: E Bu TLEB Patented Nov. 4,1919.

GEORGE 2. Burma, or LEBANON, NEW HAMPSHIRE.

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To all whom it may concern:

Be it known that I, GEORGE P. BUTLER, a

citizen of the United Statesfresiding at Lebanon, in the county ofGrafton and State of New Hampshire, have invented new and usefulImprovements in Bits, of which the following is a specification.

This invention relates to improvements in I machine bits. -Moreparticularly it relates to improvements in the points of augers or otherboring tools for wood or the like. In order to perform successfully itsfunction of centering the tools, the" point of a bit must have adequatestrength, which means a considerable diameter. In ordernto penetratethewood the point is usually made more or less conical. As the cuttingparts of the bit do not make a hole for the entrance of this conicalpoint into the wood the propulsion of this conical point through thewood requires theme of pressure which develops friction that is damagingto the temper of the tool. In hand angers it is customary to erectascrew thread on the (zone, which draws in the point as thegbit isrotated; but machine bits rotate at such a speed that the use of. ascrew point is not feasible. In its place it has been customary to usesmooth points, or diamond points"; but whatever its shape a point hasto'be pushed into the wood by forceas the operator feeds the bitinto'the work. To get the best results it is customary to rotate the bitathigh speed, so that the cutters shall be able to do as much oftheir'work as possible before the momentum is .lost. So much friction.results that the point becomes heated and soon loses its temper.Furthermore a bit which has to be forced by this "being turned 90;

means is not completely under the control of the operator. It is amongthe objects of the present. invention to provide means so that thefeeding of the bit shall remain constantly and delicately under thecontrol of the operator; means by which the bit may operate successfullyat a rotatory speed considerably "below present practice," thus greatlyreducing friction; 'means by which the efiiciency of cutting is at, thesame time increased because at the lower speed thicker chips can bemade, with a shorter total distame of actual cuttingedge-t avel hro gh sfies??? of was ge Patented Nov. 4, 1919.

Application filed June 17, 1916. Serial No. 104,279.

the wood in order to accomplish a given depth of cutting; and means bywhich the effort needed to drive the point through the wood is largelytransferred to the machine, such part as remains to be executed by theoperator being well within the control of Other results obtained by theinvention, flowing from the attainment of these objects, are that thelife of the bit is prolonged the axis, starting with a needle-likesolid,

which constitutes the tip of the point, and

Y which is of such small cross-section that it can be pushed into thewood with easy efiort of the operator, or of feeding means provided inthe machine. When in operation,

no pressure is needed beyond that requisite to insert this needle tip,for the work of enlarging the hole it has made, so that the whole pointcan be housed therein, is done by'the machine because of the spiralnature of the cam, assuming of course, that the operator keeps onpushing the point. The shape of the whole point thus constitutedprovides a safety device, preventing progressat more than a certainrate.

An embodiment of the invention'is illustrated in the accompanyingdrawings in which: f

Figure lis a side view of a machine bit;

.Fig. 2' is a side view of the same after Fig. 3 is a side view of thesame with the spurnearest the eye cut away to disclose the base of thepoint.

Fig. 4 is an end view of the form shown -Fig. 5 is a side view of amodification with part cut away as in Fig. 3. 0

Referring to the drawings, 10 lndicates the shank, 11 the twist, 12 theperipheral cutting-points, and 13 the radial cutting ec es of an auger,which is the particular y e 95 medals 19. 1 sele d f stration. The pointof the bit has a helical spiral surface. Its most advanced part has atip 1 1 so small in diameter that it can be readily pressed into thestock upon which the auger is to work.

From this narrow diameter the cross sectional size of the pointincreases along a spiral to the larger size indicated at the base 15,next to the radial cutting edge 13. The spiral line 17 is seen in theend view, Fig. 4E. From this line a surface 16 extends along the axis ofthe tool, the convolution of this spiral surface being also convolutionsof a helix whose courseis defined by the same line as seen in Figs. 1, 2and '3. The said line is really the corner between the said surface andan abutment 18 which faces toward the tip of the point and has a widthdetermined by the pitch of the spiral. This width is obviously greatenough .and blunt enough to arrest the direct ad- WVhat-ever part of thepoint has penetrated merely revolves in the hole it has made until it ispushed farther in; and whenever it is pushed farther in, the hole isenlarged to receive it by the spiral component, which, because it iscompounded with a helix, becomes I of larger cross section by gentlegradation and so slowly, by comparison with the speed of rotation of thetool, that it can and does easily expand the hole. The powerfor doingthis is exerted in all-dire'ctions in planes perpendicular to the axisof the tool. Hence the force driving it has practically no component .inthe direction of said axis; and hence the force, and power, for this aresupplied practically wholly from the rotatory power of the machine, andnot from the feeding means, whether hand or otherwise, which the machinevhas for driving the point into the work. The hole being thus enlargedby the cam-like spiral surfaces acting in planes perpendicular to theaxis, the tool can itself be pushed along in the directionv of the axiswithout effort so far as the p'oint'is concerned except what is requiredto introduce the tip of the point farther into the work, which islittle.

And even this little is reduced if the very tip of the point ha anabrasive ora cutting edge and is a little eccentric so that it rotatesor revolves through a small circle about the axis, abrading the wood infront of it as it does so. The convex angular edge 17 between thesurfaces 16 and 18 1s eccentric throughout its whole length in a certainsense because of its spiral form, 71. 6., any particular point thereinis farther from the axis of revolution than is the point which isdirectly opposite it 011 the other side of the axis. Hence in therotation of the tool an abrasive effect can be attained for enlargingthe hole which the point is entering, as distinguished from the merespreading which would occur if a cone were driven in, with accompanyingdanger of splitting. Fig. 5 shows a spiral helical surface con ceived asbeing generated by an element having a shape concave toward the axis,illustrated at 16, being of this shape so that the approach of thls lineto the outer edge of the abutment 18 is at an acute angle. This makes ascraping or abrasive edge, particularly if it has some bur, so that thewood into which the point of the bit is being ad vanced is more or lessabraded.

As every physicalpoint in the combined spiral and helical line markingthe apex of this angle between surfaces 18 and 16 is thus off-center,these points the -aggregate being on all sides of the axis, the point asa whole runs true, the eccentricity of any one part being balanced bytheeccentricity of others all around the axis. It will be noticed that theangle between the surfaces 16 and 18 is too blunt to act as a screw,because the surface 16 at any given point has a radius approximatelyequaling the radius of the extreme outer edge of the surface 18 directlyin front of it; and this fact, taken in conjunction with the rapidrotation of the tool, makes the edgeact more as a scraper. The smallchips from this can come away through the concave face of the surface16. Moreover,as the bit rotates its point isnot in contact with the woodin which it is embedded except on'the spiral, helical line which formsthe outer limit of the abutment 18. Hence the friction and the generatedheat are not as great as in the casevof smooth conical point, whoseentire surface is pressed and rubbing close against the wood. 7

Variations may be made from the precise forms illustrated withoutdeparting from thescopeof the invention. It is intended to cover bysuitable expression in the appended claims whatever features ofpatentable novelty exist in the invention disclosed.

.'. I clainr as my invention:

1. A b1t;for high rotative speed woodborlnghavmg a point with needle tipand with lateral surface approximately parallel to the'axis andextending in a spiral and hehcal course backward from the said tip tothebase of the point.

2. A bit for high rotative speed wood-borthe abutment and approximatelyequals it ing having a point with needle tip and with in radius; with anabrading edge between surface back of the tip composed of two saidelements. elements, each spiral and helical, one of Signed by me atLebanon, New Hamp- 10 5 which is an abutment facing forward, and shire,this tenth day of June, 1916.

the other of which is behind the crest of GEORGE P. BUTLER.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

7 Washington, II. 0.

